The present invention relates to change-speed gearing units for motor vehicles, and more particularly to a change-speed gearing unit of the direct operation type in which a manual shift lever is mounted at its lower end on a retainer casing in such a way as to be selectively shifted, the retainer casing being secured at its outer peripheral portion to the upper seating face of an extension housing for the unit by means of a plurality of fastening bolts threaded into the housing with intervention of an oil buffer or interseptum member of elastic material between the outer peripheral portion of the retainer casing and the upper seating face of the housing.
In such a mounting construction of the retainer casing as described above, it is required to effectively absorb vibration acting on the retainer casing so as to eliminate unpleasant noises and vibrations dissipated into the passenger compartment through the retainer casing from the interior of the extension housing. It is also required to restrict relative displacements of the retainer casing with respect to the extension housing as small as possible to ensure a good operational feel in shift-and-select operation of the shift lever and to enhance the sealing effect between the extension housing and the retainer casing so as to prevent oil leakage from the fitted portion between the buffer member and the upper seating face of the housing.